Field of the Application
The invention relates to a polyester, and more particularly, to a biodegradable polyester.
Description of Related Art
In recent years, there has been renewal of interest in development of biodegradable polyester due to that can be considered an alternative to conventional non-biodegradable plastics and a viable way in reducing pollutions originating from plastic wastes, after use when it enters the waste system. Biodegradable polyesters are degraded and catabolized by microorganism enzymes such as lipase or esterase, able to cleave polymeric molecules reducing progressively their molecular weight, as well as metabolism to carbon dioxide and water are produced during composting conditions. Generally, the development of biodegradable polymer should be considered its characterization such as physical, thermal, mechanical properties and biodegradability for using in commercial application. A series of biodegradable plastics based on low cost biomass (e.g. starch or cellulose) blending with biodegradable polyesters have been developed in order to improve its cost competitiveness whilst maintaining their mechanical properties at an acceptable level.
The biodegradable polyester plays a very important role in applications of biodegradable plastic or biomass plastic. Most biodegradable plastics adopt biomaterials as sources, and are obtained through compounding or polymerizing. For example, starch compounded plastics adopt starch as a raw material, a polylactate (PLA) adopts lactic acids of a microbial fermentation as a raw material, a microbial polyester adopts a polyhydroxyalkanoates (PHA) obtained in the microbial fermentation as a raw material. Generally, an adding amount of the biodegradable polyester in the biodegradable plastics may be up to more than fifty percent. An important function of the biodegradable polyester is to improve an essential too high or too low melting temperature of various materials (e.g., starch, PLA or PHA) in the biodegradable plastics, or adjust defects in mechanical strength thereof, such as problems in insufficient tensile strength, ductility or tensile elasticity, or poor hardness. In addition, when improving the hot melt property and the mechanical strength of the biodegradable plastics, the biodegradable polyester does not affect the biodegradability of the biodegradable plastics, and may even adjust a degradation time of the biodegradable plastics, so as to expand the applications and the economic benefits thereof in exploiting the different markets.
Ranges of applications of the biodegradable plastics are very broad, and mainly include application fields that are difficult to recover or with limited success in recycling, fields of certain professional purposes, and products applied in the natural environment. In detail, the application fields that are difficult to recover or with limited success in recycling include personal hygiene products, food packaging materials and daily commodities, such as shopping bags, strappings, bottles, cosmetic containers, pens, pencil boxes, lightweight raincoat, fresh food packaging trays, fast food containers (bowls, plates, soup cups, boxes), plastic wraps, packaging bags, garbage bags, food waste bags, toothbrushes, disposable underwear, food packaging films and beverage packaging material, 3C home appliance casings and anti-static bag, and so forth. Particular medical uses includes biodegradable and absorbable or slow-release materials, such as materials for sustained-releasing drugs, dental plastics, bone plates, bone screws (pin, bolt, hook ring and so forth), surgical sutures, medical sponges, gauzes, wound dressings, nerve guides, blood vessel substitutes, disposable medical equipments and rehabilitation supplies, and so forth. In addition, it also includes agricultural applications, such as agricultural films and utensils, containers of pesticides or fertilizers, delivery materials, and so forth. Products applied in the natural environment includes civil engineering and construction materials or outdoor leisure goods, for example, the vegetative cover nets, retaining nets, soil and water conservation cloth materials, golf tees, fishing tackles, hiking supplies or ocean sports supplies. After many of the aforementioned products have adopted the biodegradable plastic materials, the indecomposable plastics that have caused serious pollutions to the environment may be replaced, and thus have a significant contribution to the environmental protection. Therefore, exploitations of the biodegradable polyester are substantially key researches for developing the biodegradable plastic materials, and have become an important industry in the future.